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This work explores the vibrational state-selective photoassociation (PA) in the ground state of the HX (X = F, Cl, I) molecule by solving the time-dependent Schrödinger equation. For the three systems, the vibrational level of is set to be the target state and the PA probability of the target state is calculated and compared by considering different initial collision momentums. It is found that the PA probabilities are in accordance with Franck-Condon overlap integral for the HI and HCl systems, but it is not the case for the HF system. Moreover, for the HF system, it is shown that the PA probability of the target state is largest and the multiphoton transition is more likely to occur. This work compared the photoassociation dynamics of the HX (X = F, Cl, and I) systems by using the time-dependent wave packet method. The PA probabilities are in accordance with Frank-Condon overlap integral for the HI and HCl systems, but it is not the case for the HF system. Moreover, for the HF system, it is shown that the PA probability of the target state is largest and the multiphoton transition is more likely to occur. [ABSTRACT FROM AUTHOR]

We present a Gaussian wavepacket approach for curve-crossing dynamics that only requires a single Gaussian wavepacket per surface. Unlike other Gaussian wavepacket approaches to curve-crossing dynamics, the present method does not rely upon probability density being built up on a non-adiabatically coupled surface by the break-up of an evolving wavepacket. Thus, our trial solution for the time-dependent Schrodinger equation comprised of a single Gaussian wavepacket per non-adiabatically coupled surface. We also present a generalization of the method to treat multi-dimensional systems that is based on the time-dependent Hartree approximation. We present numerical results for both single and multi-dimensional curve-crossing dynamics and compare them to the exact results. [ABSTRACT FROM AUTHOR]

The present paper shows the failure of CS (centrifugal sudden or coupled states) approximation in the time-dependent (TD) quantum wave packet calculation for the exoergicity reaction O + NH on the 1A′ potential energy surface [Guadagnini, Schatz and Walch, J Chem Phys102:774 (1995)] that has double deep wells. In order to show this, total reaction probabilities and rate constants for the title reaction are presented in this study with the CS approximation and the CC (close-coupling) method, respectively. The results show that by carrying out the wave packet propagation to several picoseconds with the CC method, we can resolve all the resonance features for the title reaction and the differences between the CS and the CC become larger as J becomes larger. When J becomes larger the agreement between the CS and the CC gets progressively worse. The failure of the CS approximation can be explained with the results of double deep wells, which cause long propagation time and make the coupling of K states important. [ABSTRACT FROM AUTHOR]